Nice question. I'm not too impressed with the answer though. I got it "right" because I picked the answer closest to correct, but it's not actually correct. There are things I need to do to make replication work with a mirror. First, I need to set up distribution for the mirror, so call sp_adddistpublisher at the publisher (to add the mirror as a publisher) and then call sp_adddistributor at the mirrer (to point at the shared distributor). Then I need to tell all the agents that connect to the publisher about the mirror, by setting the -PublisherFailOverPartner agent parameter for each agent, and restarting them. Assuming this is transactional replication without update this has to be done for the log reader agent and the snapshot agent. If it's some other kind of replication I will also need to do this for one or more of the Queue Reader Agent and various sorts of merge agent (I would have to consult BoL to determine which). That's a far cry from "you don't need to do anything, it's handled automatically"; of course once I've done those things, fail over will be handled automatically for me.

I almost picked the "correct" answer but then thought that there are a number of steps and commands that need to be executed on the mirror before replication could work. I would agree with Tom that the "correct" answer was not actually the right answer. Thanks for the question anyway.